The present invention relates to an optical liquid level gauge and, more particularly, to an inexpensive gauge of this type which enables the level of a liquid in a relatively deep tank to be monitored.
Liquid level gauges have been designed in the past which rely for depth detection on the refraction of light from a light transmitting probe when the probe contacts or becomes submerged within a liquid. Devices of this nature employing optical probes have significant advantages in principle over the mechanical and electrical type devices now commonly used to detect the level of a liquid in, for example, a fuel tank. Such devices generally eliminate the necessity for moving parts; reduce fire or explosion danger; and are able to withstand rolling and pitching motion such as that found on boats, without damage. The difficulty with most devices of this type, though, is that relatively expensive optical probes, such as ones made up of a plurality of fiber optic strands, are generally required to transmit light over a sufficient distance to enable depth measurements at reasonable tank depths. For this reason, such devices have not replaced, to any significant degree, the mechanical or electrical types of devices found in, for example, the fuel tanks of consumer oriented vehicles such as automobiles and pleasure boats.